1. Field of Invention
The present invention relates to a power generation system and a condenser thereof, and more particularly to an ocean thermal energy conversion (OTEC) system and a condenser thereof.
2. Related Art
With the rapid consumption of crude oil reserves in the world, renewable energies such as solar energy, wind, geothermal, ocean energy, and biomass energy having advantages such as cleanness, permanence, low carbon content, and low pollution, have gradually received worldwide attention. Among these, a closed type ocean thermal energy conversion (OTEC) plant employs Rankine cycle power system to convert the temperature thermal energy (a temperature difference) between warm surface sea water and cold deep sea water into rotational kinetic energy by a turbine, then generates an electric power by a power generator or directly outputs the shaft power.
Generally speaking, when a temperature difference between surface sea water and deep sea water in a sea area exceeds over 20° C., an OTEC plant could be used to convert the thermal energy into electric power in the conventional art. Oceans in tropical and subtropical areas are suitable for mounting OTEC plant, because the temperature of surface sea water in these areas would be as high as 25-30° C. all the year round, and the deep sea water temperature would be 4-6° C. as the water depth of these sea areas reaches 700-1000 meters.
Under the temperature conditions of the above heat source (i.e., the surface sea water) and heat sink (i.e., the deep sea water), the Carnot cycle efficiency is about 6.4%-8.5%. However, in an actual state, since the surface sea water has to transfer thermal energy to a working fluid through an evaporator, and the working fluid in turn has to release thermal energy to the deep sea water through a condenser, the heat exchange can be performed only if a temperature difference exists between the sea water and the working fluid. Moreover, since constitutional elements of a power generation system all have pressure loss and heat dissipation, the actual thermal efficiency of a conventional OTEC plant is only 2.0-3.0%.
Since the actual thermal efficiency of a conventional OTEC plant is low, the plant requires both a large amount of surface sea water and deep sea water in the conventional art to meet the demand for the rated power capacity of the plant. Since the large amount of sea water requirement, the diameter of a sea water pipe for the conventional power generation system is quite huge. Taking a 5 MW conventional OTEC plant as an example, the requirement for the surface sea water and deep sea water always exceeds 1 megaton per day respectively, provided that the efficiency of the plant is 2.5%. In this way, the pipe diameter of the sea water pipe is over 3.2 meters. While using such a sea water pipe to transport deep sea water from 700-1000 meters depth to a land-based plant, this sea water pipe encounters severe challenges such as bending stress, shear force, vibration, and warping due to the violent wave or marine current, and it is susceptibly damaged or destroyed.
Based on the above, in a conventional OTEC plant, the sea water pipe for transporting deep sea water has a high manufacturing cost (account for about 20% of the manufacturing cost of the power plant), and has a poor reliability during operation.